1. Field of the Invention
This invention relates to margarines and like edible emulsion food spreads of which the fat phase contains palm oil. It is particularly concerned with spreads which are soft enough to be spread at domestic refrigerator temperatures, including those which on account of their low fat contant are in demand in low calory diets. The more stable of these, like margarine, are of the water-in-oil variety and are similarly prepared, by chilling, working and resting the previously prepared emulsion, which may contain additional flavouring, colouring, vitamin and emulsifier components similar to those found in conventional margarine. These combined operations are nowadays carried out in a continuous fashion, in scraped surface heat exchangers of the Votator type and partially crystallise the fat to form a network in which the globules of the aqueous phase are retained, thus stabilising the emulsion against undesirable accretion of the droplets with consequent emulsion breakdown and multiplication of bacterial growth.
Both the oral response developed upon eating margarine and similar fat spread products and the textural response experienced upon spreading them are largely determined by the composition of the fat phase of the product. Great skill, much of it of an empirical nature, is needed to devise the most appropriate fat composition, often a blend of many fats, to meet these needs with economic benefit. In recent times an even more stringent requirement needs to be met for so-called soft margarines and similar spreads which can be spread directly from storage in domestic refrigerators, ie about 5.degree.C. This requirement calls for a particularly flat hardness/temperature response and is a most exacting one to meet.
2. The Prior Art
Palm oil is a cheap and abundant vegetable oil already in widespread use in the Margarine Industry. The limitations imposed upon the amount of palm oil that can be included in margarine and like fat spreads relate to its tendency to confer on fat compositions in which it is incorporated, its own slowcrystallising characteristics. This leads to the phenomenon of post-hardening in which a product that is satisfactory in its textural characteristics when it is initially prepared, subsequently hardens on storage to affect both its oral response when it is said to be grainy, and its ability to spread at ambient or lower temperatures.
Interesterification as a technique for modifying the characteristics of palm oil and to admit of its greater use in the Industry is described in "Margarine" 2nd Edition, Andersen and Williams, 1954 page 31, and the general description of the technique is given on pages 54 etc. In this and in other publications however the palm oil is corandomised with a comparable amount of a second oil, either a lauric oil, vide British Pat. No. 874,675, a C.sub.16 -C.sub.18 vegetable oil in a fat formulation that includes a substantial trans-acid content combined in the triglycerides of the fat composition.
In other references, eg Seiden U.S. Pat. No. 3,353,964, similarly a corandomised blend is disclosed, but between lauric fats and fats of long-chain acids, ie C.sub.20 -C.sub.22.
Melnick U.S. Pat. No. 2,921,855 describes a corandomised blend, used as a margarine fat, of a triglyceride oil rich in combined polyunsaturated fatty acid, with a highly hydrogenated fat, while Nelson U.S. Pat. No. 2,855,311 discloses the corandomisation of a blend of palm oil with a variety of liquid oils.
In none of these prior disclosures does any suggestion appear that a remedy to overcome the now widely-recognised problem of using palm oil in substantial quantities in emulsion spreads may lie in randomisation essentially of the oil itself, without recourse to the profound changes brought about in modifying the properties of this oil by distributing its own fatty acid moieties among those of other, distinctly different fats.
This invention relates to edible fat compositions such as margarines and shortenings in the preparation of which palm oil is used.
Palm oil is readily available and low in cost among vegetable oils and in several respects appears suitable for the preparation of edible fat products such as margarines and shortenings. Its widespread adoption for these purposes has however been handicapped in the past by its slow rate of crystallisation, with the result that, long after processing has been completed products containing palm oil undergo hardening and suffer other undesirable changes caused by the continued crystallisation of the oil.
It has now been found that margarine products containing substantial quantities of palm oil may be prepared by randomising the palm oil and preparing a fat blend therewith.
Preferably the palm oil is randomised alone, but it may be corandomised with small amounts, not exceeding 10 weight % and preferably less than 5 wt %, of other edible oils or fats, whether of vegetable or animal origin, including marine oil. Similarly, although the palm oil may be modified somewhat by fractionation or other treatment before being randomised, this should essentially impose no major modification upon the inherent characteristics of the fat.
It is indeed an important feature of the invention that the fatty acid composition of the oil remains unchanged, in contrast to the effect of using fractionation methods. Similarly, the glyceride composition of other fats present in the products of the invention remain unchanged, in contrast to corandomisation methods which change the glyceride composition of both the palm and the other corandomised fats. For example, the glyceride components of palm oil may be separated into a high melting stearine fraction and a low melting oleine fraction by subjecting palm oil to fractional crystallisation, the compositions of the fractions differing markedly, to an extent depending upon the conditions of the crystallisation. In accordance with U.S. pat. No. 3,189,465 an oleine fraction obtained in this way is blended with other fats in margarine formulations. Again, stearine and oleine fractions may be obtained by subjecting palm oil to directed interesterification, carried out under conditions favouring the continued formation of a limited range of glycerides, usually a stearine fraction separated from the liquid phase by carrying out the process at comparatively low temperatures. The stearine and oleine fractions obtained in this way, while again differing markedly from one another, are composed essentially of different combinations of the fatty acids of the oil and thus contain different glycerides from those originally present. The stearine fraction obtained in this way has been proposed for use in shortening compositions.
In both fractionation and directed interesterification methods a substantial proportion of the palm oil is discarded. The disadvantages described may also be overcome, while utilising whole palm oil, by subjecting it to hydrogenation, but the resultant change in glyceride composition that this brings about leads to unsatisfactory melting characteristics in margarine and similar food spreads by producing a cloying sensation in the mouth due to the presence of higher melting glycerides.
A further advantage of the invention is that no other fat need be involved in the interesterification. This again provides substantial economies and permits the use, in blends with the randomised palm oil, of other fats in proportions providing optimum melting characteristics whose own melting characteristics are unmodified by corandomisation with the palm oil. The cool-melting characteristics of lauric fats for example, which may be present in the products of the invention are accordingly retained, since they are blended instead of being corandomised with palm oil in accordance with earlier proposals.
The invention is particularly useful in the preparation of margarine and like emulsion fat spreads, which are often required to meet rigid product specifications, especially as to their melting and hardness characteristics. In particular, the so-called soft margarines now in vogue are required to remain easily spreadable, as table margarines, at domestic refrigerator temperatures, ie about 5.degree.C, while yet being of plastic consistency at ambient temperatures, which may be as high as 20.degree.C. These requirements imply a flat response to temperature of hardness value. If this is measured in accordance with the penetration method of Haighton, then a soft margarine may be described as one having the penetration range from C.sub.4 less than 900 g/cm.sup.2 and particularly less than 750 g/cm.sup.2, to c.sub.20 between 50 and 150 g/cm.sup.2 according to the time of year. A very small amount of whole or modified palm oil is permissible in soft spreads, at most about 10 wt % beyond which the product tends to unacceptable hardness.
The invention is particularly suitable for the preparation of fat blends for soft margarines, meeting the above requirements for hardness values with as much as 40 wt %, in contrast to conventional formulations in which not more than 25 wt % is practical in spread formulations, many of which nevertheless fail to meet the above-stated requirements for soft spreads, unless a substantial quantity, often as much as 40 wt % or even more, of an expensive liquid vegetable oil, for example sunflower oil, is also present. A particular advantage in the invention is that not only is less oil of this kind necessary, but it may be totally replaced by cheaper oils, for example soybean oil. Preferably the fat compositions of the invention contain from 15 to 30 wt % palm oil, preferably about 20-25 wt %. The dilatation values of palm oil increase with randomisation, and amounts in excess of 40 wt % are therefore less desirable.
In addition to meeting the above penetration characteristics, the fat component of soft spreads is also required, for good consumer response to fulfil palatability requirements provided by melting characteristics that may be expressed by dilatation values measured in the manner described in J. Am. Oil Chem. Soc. (1954) 31, pp. 98-103. These should lie between about D.sub.5 = 600 and D.sub.35 below 50. These requirements are met largely by an appropriate choice of fats or oils with which the randomised palm is blended, and hardness also by adjustment of the conditions under which the fat emulsion is processed. In accordance with contemporary practice, the spreads of the present invention are preferably prepared from an emulsion of an aqueous phase in the fat phase, followed by chilling and working the composition to crystallise the fat, in "Votator" equipment including a scraped surface heat exchange chiller. Other things being equal, greater amounts of palm oil may be incorporated using longer residence times in the Votator.
In addition to palm oil, the fat blends of the invention may include a variety of other components. A proportion of unrandomised palm oil may for example be present, but this should desirably not exceed 10%, since it induces post-processing hardening during the shelf-life of the spread, particularly within a few hours of manufacture. Similarly the presence of unrandomised hardened palm or palm fractions should not exceed 10 wt %.
Other semi-solid fats of the palmitic variety, eg cottonseed oil, may be included in similar quantities and lauric fats, eg palm kernel oil, babassu and coconut oils and their fractions, are all suitable components. Several animal fats rich in palmitic acid are also suitable, eg lard and tallow; others include marine oils, for example herring and sardine oils, although these in 10% with general practice may require hardening treatment by hydrogenation to confer flavour stability. Again, however, preferably not more than 10% and particularly not more than 5% by weight of these fats should be present in the fat composition.
The major part, ie more than 50 wt % of the fat component of the spreads according to the invention is composed of vegetable oils which at ambient temperatures, ie 15.degree.C are liquid, or which are lightly hydrogenated to a melting point of 15.degree.-30.degree.C. These comprise for example corn, groundnut, safflower, sunflower, sesame and soybean oil. The latter in particular, being cheap is preferred. In keeping with widespread practice, it is preferably hydrogenated at least in part to stabilise the oil against deterioration, although the oil may remain largely unsaturated, with an Iodine Value of 90 or more. Besides meeting the requirement for producing soft, palatable spreads, the choice as well as the amount of liquid oil is preferably governed by the widely accepted desirability of incorporating within the composition glycerides of the polyunsaturated, socalled essential acids. Preferably the fat compositions of the invention consist of randomised palm oil and a fat or fat blend having a melting point of 25.degree.-30.degree.C. In this specification the melting point of a fat means the temperature at which the fat becomes wholly melted, shown by slowly heating the fat until it turns clear.
It will be understood that the invention may be applied in the preparation of margarine and of other spreads having a lower fat content than is required in margarine. These socalled low fat spreads may contain as little as 40 wt % fat. The invention is also applicable to shortening compositions in which whole randomised palm oil is blended.